Aib-rich peptides containing lactam-bridged side chains as models of the 3(10)-helix

J Am Chem Soc. 2001 Mar 28;123(12):2743-51. doi: 10.1021/ja0027261.

Abstract

Aib-rich side chain lactam-bridged oligomers with n =1, 2, 3, were designed and synthesized as putative models of the 3(10)-helix. These peptides were conformationally characterized in aqueous solution containing SDS micelles by CD, NMR, and computer simulations. The lactam bridge between the side chains of L-Glu and L-Lys in (i) and (i+3) positions was introduced in order to enhance the conformational preference toward the right-handed 3(10)-helix. The NMR results clearly indicate that there is an increase of 3(10)-helix formation upon chain elongation. In the dimer and trimer (n = 2 and n = 3, respectively, in the structure reported above) the observed NOE connectivities are compatible with the 3(10)-helical arrangement, confirmed by the temperature coefficients of the amide proton resonances which suggest the presence of a hydrogen-bonded structure. The phi and psi dihedral angles of the structures obtained by molecular dynamics calculations are also compatible with the 3(10)-helix. Identification of the hydrogen-bond pattern indicate that C=O(i)- - -HN(i+3) hydrogen bonds, typical of the 3(10)-helical conformation, are highly probable in all low-energy structures. The CD spectra of these Aib-rich lactam-bridged oligopeptides, obtained in the same solvent system used for NMR experiments, provide important insight into the spectroscopic characteristics of the 3(10)-helix.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry
  • Circular Dichroism
  • Lactams / chemistry*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Peptides / chemical synthesis
  • Peptides / chemistry*
  • Protein Structure, Secondary*
  • Solutions / chemistry

Substances

  • Anti-Bacterial Agents
  • Lactams
  • Peptides
  • Solutions